Role of CCL2/MCP-1 in mucosal immunity to Toxoplasma

描述（由申请人提供）：弓形虫是一种主要的艾滋病相关病原体，可导致先天性感染婴儿严重疾病或死亡。该寄生虫也被归类为NIAID B类优先微生物。本申请的长期目标是了解控制这种机会性原生动物病原体感染所必需的细胞免疫应答机制，并确定功能失调的应答如何导致免疫病理学和无法控制感染。初步数据表明，缺乏趋化因子MCP-1（CCL 2）表达的小鼠对T.这与共表达Gr-1和MHC II类以及共刺激分子CD 80/CD 86和CD 40的单核细胞/树突状细胞样群体向腹膜腔的募集缺陷有关。其他最近的研究也描述了类似的细胞，尽管它们是否介导保护或增加易感性尚不清楚，可能取决于感染模型。本研究的目的是确定在弓形虫口腔感染的粘膜免疫应答过程中是否招募了MHC II类和Gr-1（MHC 2 +Gr-1+）双阳性细胞。我们将采用以下具体目标来解决这一问题。1.确定与腹膜内感染相比，CCL 2缺乏在口腔感染期间的影响，特别是趋化因子是否介导对弓形虫的抗性或易感性，以及CCL 2缺乏是否改变感染期间的Th 1/Th 2平衡。2.确定CCL 2在对感染的粘膜免疫应答期间是否募集MHC 2 +GR-1+细胞。还将检查这些细胞作为感染储库和表达杀微生物分子和细胞因子（特别是IL-12）的能力。这些目标将通过从肠粘膜组织分离的细胞的离体和体外分析来实现。将通过荧光免疫组织化学实现野生型和CCL 2阴性小鼠肠粘膜中MHC II类阳性和Gr-1阳性细胞的直接可视化。这些研究有望加深我们对弓形虫免疫如何在粘膜组织中启动的理解，并将阐明MHC 2 +Gr-1+细胞在这一过程中的作用。了解免疫是如何被触发的，最终将导致更有效的手段来控制弓形虫和其他口腔传播的艾滋病相关微生物病原体的感染。该项目与公共卫生的相关性是，弓形虫感染了全世界30-80%的人口。虽然通常是无症状的感染，但由于免疫功能不佳，寄生虫会成为一种毁灭性的，有时是致命的感染。该项目将提高我们对寄生虫免疫力的理解，从而改进治疗策略。

DESCRIPTION (provided by applicant): Toxoplasma gondii is a major AIDS-associated pathogen that can cause severe disease or death in congenitally infected infants. The parasite is also classified as an NIAID Category B priority microorganism. The long-term objective of this application is to understand the cellular immune response mechanisms that are necessary to control infection with this opportunistic protozoan pathogen, and to determine how dysfunctional responses can lead to immunopathology and inability to control infection. Preliminary data indicate that mice lacking expression of chemokine MCP-1 (CCL2) are highly susceptible to intraperitoneal infection with T. gondii, and this is associated with defective recruitment into the peritoneal cavity of a monocyte/dendritic cell- like population co-expressing Gr-1 and MHC class II and costimulatory molecules CD80/CD86 and CD40. Other recent studies have described similar cells, although whether they mediate protection or increase susceptibility is not clear and may depend upon the infection model. The goal of the present proposal is to determine whether cells double-positive for MHC class II and Gr-1 (MHC2+Gr-1+) are recruited during the mucosal immune response to oral infection with Toxoplasma. The specific aims we will employ to address this issue are as follows. 1, Determine the effects of CCL2 deficiency during oral infection compared to intraperitoneal infection, in particular whether the chemokine mediates resistance or susceptibility to Toxoplasma, and whether lack of CCL2 alters the Th1/Th2 balance during infection. 2, Determine if CCL2 recruits MHC2+GR-1+ cells during the mucosal immune response to infection. The ability of these cells to serve as an infection reservoir and to express microbicidal molecules and cytokines (in particular, IL-12) will also be examined. These aims will be achieved by ex vivo and in vitro analyses of cells isolated from intestinal mucosal tissues. Direct visualization of MHC class II-positive and Gr-1-positive cells in intestinal mucosa of wild-type and CCL2 negative mice will be accomplished by fluorescence immunohistochemistry. These studies can be expected to deepen our understanding of how immunity to Toxoplasma is initiated in mucosal tissues and will clarify the role of MHC2+Gr-1+ cells in this process. Understanding how immunity is triggered will ultimately lead to more effective means of controlling infection with Toxoplasma and other orally transmitted AIDS-associated microbial pathogens. The relevance of the project to public health is that Toxoplasma infects between 30-80% of the human population worldwide. While normally an asymptomatic infection, with suboptimal immune function the parasite emerges as a devastating and sometimes lethal infection. This project will enhance our understanding of immunity to the parasite, leading to improved treatment strategies.